prepost/lib/pre.js

Alter arguments and return values before and after a function is called

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = pre;

function _toConsumableArray(arr) { if (Array.isArray(arr)) { for (var i = 0, arr2 = Array(arr.length); i < arr.length; i++) { arr2[i] = arr[i]; } return arr2; } else { return Array.from(arr); } }

var preCallNoop = function preCallNoop() {
  for (var _len = arguments.length, args = Array(_len), _key = 0; _key < _len; _key++) {
    args[_key] = arguments[_key];
  }

  return args;
};

// Alter the arguments before they are passed to the function
function pre() {
  var _ref;

  for (var _len2 = arguments.length, args = Array(_len2), _key2 = 0; _key2 < _len2; _key2++) {
    args[_key2] = arguments[_key2];
  }

  // Flatten args so that pre functions can be passed as arrays
  args = (_ref = []).concat.apply(_ref, _toConsumableArray(args));

  if (args.length < 2) {
    throw new Error('Two arguments required');
  } else if (args.length > 2) {
    args = [args[0], pre.apply(undefined, _toConsumableArray(args.slice(1)))];
  }

  var preFn = args[0] || preCallNoop;

  if (typeof preFn !== 'function') {
    throw new TypeError('Pre function must be a function');
  }

  var callFn = args[1];

  if (typeof callFn !== 'function') {
    throw new TypeError('Function to call must be a function');
  }

  return function () {
    for (var _len3 = arguments.length, args = Array(_len3), _key3 = 0; _key3 < _len3; _key3++) {
      args[_key3] = arguments[_key3];
    }

    args = preFn.apply(undefined, _toConsumableArray(args));

    if (Array.isArray(args)) {
      return callFn.apply(undefined, _toConsumableArray(args));
    }

    // Args can be a promise which should be resolved before callFn is called
    return args.then(function (args) {
      return callFn.apply(undefined, _toConsumableArray(args));
    });
  };
}